Adam Lambert has treated fans to a picture of himself with Sir Elton John.

The two acts performed at the iHeart Radio Music Festival on Friday (September 20) in Las Vegas.

The 'Trespassing' star on Sunday (September 22) uploaded a photo to Instagram of himself with the piano legend, adding:

"#eltonjohn #duckface...His Vegas show is soooo good."

John currently has a Las Vegas residency called 'The Million Dollar Piano', which is taking place at Caesars Palace's Colosseum.

He recently released new album 'The Diving Board', which hit No.3 in the UK chart.